1. Field of the Invention
This invention relates to an imaging apparatus which comprises a camera body and a lens unit (an interchangeable lens unit) capable of being mounted on and removed from the camera body and which photographs a subject image via the lens unit on the camera body side.
2. Description of the Related Art
One known imaging apparatus is a camera with interchangeable lenses which comprises a camera body and a lens unit capable of being mounted on and removed from the camera body. The lens unit includes a focusing lens for adjusting the focal position to bring a subject image into focus. The camera body is provided with an imaging device which photographs a subject image formed by the lens unit. For example, Jpn. Pat. Appln. KOKAI Publication No. 2-135406 has disclosed a camera system which effects communication between the camera body and the interchangeable lenses in synchronization with the vertical synchronization signal of the imaging device. Jpn. Pat. Appln. KOKAI Publication No. 2007-228047 has disclosed use of a CMOS sensor as an imaging device in a recent digital camera.
Such an imaging device performs a contrast autofocus (AF) operation in photographing the subject image. In contrast AF, the contrast value (AF evaluated value) in an A area of the photographed image is obtained on the basis of the output signal of the imaging device, while the position of the focusing lens is being changed. The position where the contrast value is the largest is set as the in-focus position.